Objective having long back focal distance with regard to its focal length

ABSTRACT

A photographic objective having a relatively long back focal distance with regard to its focal length and also having a great relative opening. The objective comprises in front of the diaphragm a negative lens element consisting of two component lenses and spaced therefrom a cemented positive lens element which consists also of two component lenses. The latter lenses have inverse refractive power. Behind the diaphragm a negative lens element is disposed which consists of three component lenses of which the middle one is a cemented lens.

Inventors Appl. No.

Filed Patented Assignee Priority Walter Mandier;

Garry Edwards; Erich Wagner, all oi Midland. Ontario, Canada Apr. 14,1970 Aug. 24. DH

Ernst Leltz G.m.b.H.

Wetzlar, Germany Apr. 26, 1969 Germany Continuation-impart ofapplication Ser. No. 833,063, June 13, 1969.

OBJECTIVE HAVING LONG BACK FOCAL DISTANCE WITH REGARD TO ITS FOCALLENGTH 1 Claim, 1 Drawing Fig.

US. Cl

[51 Int. Cl G02b 9/62 [50] Field of Search 350/209, 214, 215. 225, 210

[56] References Cited UNIT ED STATES PATENTS 3,132,199 5/1964Zimmerrnann et al Primary Examiner- David Schonberg Assistant Examiner--Paul A. Sacher Anomey-Krafl't & Wells ABSTRACT: A photographic objectivehaving a relatively long back focal distance with regard to its focallength and also having a great relative opening. The objective comprisesin front of the diaphragm a negative lens element consisting of twocomponent lenses and spaced therefrom a cemented positive lens elementwhichconsists also of two component lenses. The latter lenses haveinverse refractive power. Behind the diaphragm a negative lens elementis disposed which consists of three component lenses of which the middleone is a cemented lens.

PATENTEU AUB24|97| v WALTER MANDLER G'ARRY EDWARDS ERICH wmwzw wvEr/mrcW OBJECTIVE HAVING LONG BACK FOCAL DISTANCE WITH REGARD TO ITS FOCALLENGTH C ROSS-REFERENC E TO RELATED APPLICATIONS This application is acontinuation-in-part of Ser. No. 833,063, filed June I3. 1969 for whichpriority under 35 USC 1 l9 was claimed for application Ser. No. P 17 72665.7 filed in the Patent Otfice of the Federal Republic of Germany onJune 15, I968. Priority under 35 USC 1 I9 is claimed in the presentapplication for application Ser. No. P l9 2] 4 l 8.7 filed in the PatentOffice of the Federal Republic of Germany on Apr. 26, 1969.

BACKGROUND OF THE INVENTION The field of the present invention isphotographic objectives. The invention is particularly concerned withwide-angle objectives having a long back focal distance and a greatrelative opening.

It is well known in the art that the use of wide-angle objectives incombination with many apparatuses and devices is facilitated to aconsiderable degree if the objectives do have a rather long back focaldistance.

Copending application Ser. No. 833,063 filed June 13. I969, of whichthis application is a continuation-in-part, describes a type ofobjectives which has the required long back focal distance and whichalso has a great relative opening. These objectives comprise a negativelens element in front of the diaphragm and a positive lens elementspaced therefrom. Behind the diaphragm a negative lens element isdisposed. The lens elements may consist of two or more component lenseswhich may be cemented together.

SUMMARY OF THE INVENTION In accordance with the present invention afurther wideangle objective of the same general optical design isprovided. The objective of our present invention comprises in front ofthe diaphragm a negative lens element consisting of two negativecomponent lenses and spaced therefrom a positive lens element consistingof two cemented component lenses which have inverse refractive power.Behind the diaphragm a negative lens element is arranged consisting ofthree negative component lenses of which the middle one is in itself acemented lens.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is an axial sectional viewof the invented objective. The applied reference symbols refer to thelens radii, spacings and lens thicknesses given in the followingexample.

DESCRIPTION OF THE PREFERRED EMBODIMENT The following example gives thedata of the invented objective:

EXAMPLE I e a a|=0.084 1 1.58482 40.58 n=+o.s11 l EXAMPLE Continued Ilata -0. 073 1. 56295 46. 88 ln=-0. 438

. a =0. 005 I lm=-4, 660

Bi0=0. I61 1. 72340 50. 17 I =-0. 331

1 Diaphragm space.

It has been found that like objectives of good correction will beachieved if variations of the refractive power of the surfaces do notexceed the amount of 0.4- l/ f and also if the variations of the lensspacings remain inside a distance of 0.05f. This is, of course, not tobe understood in a sense that all parameters may vary at the same timein the same direction, but that the variation of one parameter in onedirection inside the mentioned boundaries may be compensated for by thevariation of one or more other parameter, which latter variations willthen also remain inside the limits set forth above.

What is claimed is:

l. A photographic objective having a relatively long back focal distancewith regard to its focal length and a great relative opening, of whichobjective the data of the lens radii, lens spacings and lens thicknesseshave substantially the following specifications:

1. A photographic objective having a relatively long back focal distancewith regard to its focal length and a great relative opening, of whichobjective the data of the lens radii, lens spacings and lens thicknesseshave substantially the following specifications: